IN mid-March my 85-year-old father checked into a prominent New York City hospital for a scheduled operation. The procedure, to remove a cancerous tumor from his thigh, went well, and soon he was sent home.

But three days later, unable to cope with a complicated wound care regimen, he landed back in the hospital.

My father had become part of a notorious trend. Discharge from the hospital is a critical point in a patient’s recovery, particularly for older people with chronic conditions. The process is supposed to be carefully planned, but instead it often is rushed and poorly coordinated, resulting in complications that send patients back to the emergency room.

According to a study published last year in The New England Journal of Medicine, one in five Medicare patients returns to the hospital within 30 days of being discharged. The problem is an expensive one: in 2004, these readmissions cost Medicare $17.4 billion dollars, the researchers also found.